Suppress warning on Fedora 17/18 (const correctness)


git-svn-id: https://root.cern.ch/svn/root/trunk@48707 27541ba8-7e3a-0410-8455-c3a389f83636
Const cast warning, again.


git-svn-id: https://root.cern.ch/svn/root/trunk@48708 27541ba8-7e3a-0410-8455-c3a389f83636
GenericValue::op= is smart; it takes *this into account.
That won't work for construction; so replace with placement new.
Also need default c'tor for Value() to initialize m_GV correctly.


git-svn-id: https://root.cern.ch/svn/root/trunk@48709 27541ba8-7e3a-0410-8455-c3a389f83636